A strong need exists in science and technology for new macromolecular materials with specifically tailored properties for a wide variety of purposes. These materials can be provided through the synthesis of new macromolecules or by the combination of existing macromolecular materials in alloys or composites to give new materials that exhibit a combination of the properties of the component macromolecules, or perhaps new properties. A number of multi-component polymer systems are known, including graft and block copolymers, filler-reinforced polymers, polymer blends (alloys), polymer laminates, and interpenetrating polymer networks (IPNs).
Polymer blends or alloys are physical mixtures of two or more polymers. The component macromolecules are held together by noncovalent intermolecular interactions such as hydrogen bonding, dipole-dipole interactions, or van der Waals forces. The strength of the interactions depends on the functional groups in the macromolecules. The roles played by different functional groups in these interactions has been reported in detail for organic polymers. Coleman, M.; Painter, P. C. Fourier Transform Infrared Spectroscopy. Appl. Spectrosc. Rev. 1984, 20, 256-346; Painter, P. C. Macromolecules 1988, 21, 666; Painter, P. C. Macromolecules 1989, 22, 570; Painter, P. C. Macromolecules 1989, 22, 580; Olabisi, P.; Robeson, L. M.; Shaw, M. T. Polymer-Polymer Miscibility; Academic Press: New York, 1979, p. 207 and references therein.
Polymer blends can exist as miscible one-phase systems, as semimiscible systems that have miscible domains which exist together with phases rich in one of the constituent polymers, or as immiscible multi-phase materials systems. In a miscible blend, the interactions between the two different components are presumably stronger than the interactions between the individual molecules of a single species. In an immiscible blend, the reverse is true. Many examples exist of miscible and immiscible polymer blends. An example of a miscible blend is that between polycaprolactone and poly(vinyl chloride), in which the blend is apparently stabilized by intermolecular hydrogen bonding between the Cl--C--H unit of the poly(vinyl chloride) and the proton-accepting character of the carbonyl group of the polycaprolactone. Olabisi, O. Macromolecules 1975, 8, 316.
Weakly interacting miscible blends can undergo phase separation over time. In fact, phase separation can be used as a measure of the weakness of intermolecular interactions between the constituent materials. The degree of separation can be determined by comparing characterization data from freshly prepared polymer blends with those prepared previously.
Polyphosphazenes are a relatively new class of inorganic polymers that contain a flexible backbone of P--N repeating units and two organic, inorganic, or organometallic groups attached to each phosphorous atom. These polymers can be prepared by the thermal ring opening polymerization of hexachlorocyclotriphosphazene to form poly(dichlorophosphazene) which is employed as a reactive macromolecular intermediate. The chlorine atoms in this polymer can be replaced via nucleophilic substitution reactions using, for example, alkoxy, aryloxy or amino reagents to give stable poly(organophosphazene) derivatives.
Polyphosphazenes exhibit a wide variety of physical and chemical properties which are a function of the substituent groups on the phosphorus atoms. For example, polyphosphazenes can be prepared that have flame-retardant properties, high resistance to oil and solvents, high backbone and materials flexibility, fiber and film forming properties, biodegradability, ceramic properties, non-linear optical utility, low temperature elastomeric properties, biomaterials, polymeric drugs, polymeric delivery systems, hydrogels, liquid crystals, and electrical semiconductors.
In the thesis of Paul E. Austin (Polyphosphazenes, New Biomaterials, Penn State University, 1984), the following polymer blends were reported:
(i) [NP(OCH.sub.2 CF.sub.3).sub.2 ].sub.n (referred to as poly[bis(trifluoroethoxy)phosphazene)] with poly(methylmethacrylate), poly(vinylpyrrolidone), and phenoxy resin; and (ii) [NP(HNCH.sub.3)2].sub.n (referred to as poly[bis(methylamino)phosphazene]) with poly(vinylpyrrolidone), poly(acrylic acid), poly(vinyl alcohol), and methyl cellulose. No miscibility testing was done on these materials. Blends of poly[bis((methoxyethoxy)ethoxy)phosphazene] (MEEP) with poly(ethylene oxide) have also been widely reported in the literature.
In light of the increasing interest in new macromolecular materials with specifically tailored properties, and the versatility of phosphazene polymers, it is an object of the present invention to provide new polymer blends that include polyphosphazenes for a variety of uses.